Saturn Archives

June 10, 2013June 5, 2017 by Fraser Cain

Ten Interesting Facts About Saturn

This article comes from our archive, but we updated it with this video.

Saturn is my absolute favorite object in the night sky. When I was a child, I had a dog-eared book on the Solar System, which I read over and over, stopping and staring with wonder at the section on Saturn. How could a planet have rings of ice? What would it be like to fly out and visit the planet, to see the rings with your own eyes. How did it get all those strange moons?

When I was 14, I purchased my first telescope, a 4-inch Newtonian from a local company in Vancouver. It was summer, and one of the first planets, appearing just after sunset was Saturn. And my telescope had just enough power and magnification to resolve the planet and its famous rings. In fact, when I first looked at Saturn through the eyepiece, I couldn’t believe that I was now seeing the planet with my own eyes. It didn’t look quite like the photographs, but my imagination could fill in the gaps.

From those first observations, my fascination with astronomy and Saturn only grew, leading me to a career in science journalism. It’s funny to think how far I’ve come, and how I can trace everything back to those warm summer nights, looking at Saturn.

Think you know everything about Saturn? Think again. Here are 10 facts about Saturn, some you may know, and some you probably didn’t know.

1. Saturn is the least dense planet in the Solar System

Saturn has a density of 0.687 grams/cubic centimeter. Just for comparison, water is 1 g/cm³ and the Earth is 5.52. Since Saturn is less dense than water, it would actually float like an apple if you could find a pool large enough. Of course, why you’d want to ruin a pool with all that hydrogen, helium and ices…

2. Saturn is a flattened ball

Saturn spins so quickly on its axis that the planet flattens itself out into an oblate spheroid. Seriously, you see this by eye when you look at a picture of Saturn; it looks like someone squished the planet a little. Of course, it’s the rapid spinning that’s squishing it, causing the equator to bulge out.

While the distance from the center to the poles is 54,000 km, the distance from the center to the equator is 60,300 km. In other words, locations on the equator are approximately 6,300 km more distant from the center than the poles.

We have a similar phenomenon here on Earth, where points on the equator are more distant from the center of the Earth, but on Saturn, it’s much more extreme.

Cassini's drawings of Saturn — Cassini’s drawings of Saturn

3. The first astronomers thought the rings were moons.

When Galileo first turned his rudimentary telescope on Saturn in 1610, he could see Saturn and its rings, but he didn’t know what he was looking at. He though that the rings might actually be two large moons stuck to either side of Saturn – ears maybe?

It wasn’t until 1655 that the Dutch astronomer Christian Huygens used a better telescope to observe Saturn. He had the resolution to realize that the moons on either side of Saturn were actually rings: “a thin, flat ring, nowhere touching, and inclined to the ecliptic.” Huygens was also the first person to discover Saturn’s largest moon, Titan.

4. Saturn has only been visited 4 times by spacecraft

Only 4 spacecraft sent from Earth have ever visited Saturn, and three of these were just brief flybys. The first was Pioneer 11, in 1979, which flew within 20,000 km of Saturn. Next came Voyager 1 in 1980, and then Voyager 2 in 1981. It wasn’t until Cassini’s arrival in 2004 that a spacecraft actually went into orbit around Saturn and captured photographs of the planet and its rings and moons.

Unfortunately, there are no future plans to send any more spacecraft to Saturn. A few missions have been proposed, including such radical concepts as a sailboat that could traverse the liquid methane lakes on Titan.

5. Saturn has 62 moons

Jupiter has 67 discovered moons, but Saturn is a close second with 62. Some of these are large, like Titan, the second largest moon in the Solar System. But most are tiny – just a few km across, and they have no official names. In fact, the last few were discovered by NASA’s Cassini orbiter just a few years ago. More will probably be discovered in the coming years.

6. The length of a day on Saturn was a mystery until recently

Determining the rotation speed of Saturn was actually very difficult to do, because the planet doesn’t have a solid surface. Unlike Mercury, you can’t just watch to see how long it takes for a specific crater to rotate back into view; astronomers needed to come up with a clever solution: the magnetic field.

To determine the rotational speed of Saturn, astronomers had to measure the rotation of the planet’s magnetic field. By one measurement, Saturn takes 10 hours and 14 minutes to turn on its orbit, but when Cassini approached Saturn, it clocked the rotation at 10 hours and 45 minutes. Astronomers now agree on an average day of 10 hours, 32 minutes and 35 seconds.

7. Saturn’s rings could be old, or they could be young.

It’s possible that Saturn’s rings have been around since the beginning of the Solar System – around 4.54 billion years ago. Or maybe they’re relatively brand new compared to the age of Saturn. Astronomers still don’t fully understand the origin of Saturn’s rings.

They might have formed recently, when a 300-km ice moon was torn apart by Saturn’s gravity, forming a ring around the planet.

It’s also possible that they’re the left over material when Saturn formed in the solar nebula. The material in the rings might have gotten jostled by Saturn’s gravity, and never could pull together into a cohesive Moon.

But astronomers have also found that the ring material looks just too clean to have formed so long ago, and could be as young as 100 million years old. It’s all just a big mystery.

Credit: NASA/JPL-Caltech/Space Science Institute

8. Sometimes the rings disappear

Well, they don’t actually disappear, but they look like they’re going away. Saturn’s axis is tilted, just like Earth. From our point of view, we see Saturn’s changing position as it takes its 30 year journey around the Sun. Sometimes, the rings are fully open, and we see them in all their glory, but other times we see the rings edge on – it looks like they’ve disappeared. This happened in 2008-2009, and will happen again in 2024-2025.

9. You can see Saturn with your own eyes

Saturn appears as one of the 5 planets visible with the unaided eye. If Saturn is in the sky at night, you can head outside and see it. To see the rings and the ball of the planet itself, you’ll want to peer through a telescope. But you can amaze your friends and family by pointing out that bright star in the sky, and let them know they’re looking at Saturn.

10. There could be life near Saturn

Not life on Saturn; the planet is way too hostile to support life. But there could be life on one of Saturn’s moons: Enceladus.

Water vapour geysers on Enceladus. Credit: NASA/JPL

NASA’s Cassini spacecraft recently discovered ice geysers blasting out of Enceladus’ southern pole. This means that some process is keep the moon warm enough that water can remain a liquid underneath the surface. And wherever we find liquid water on Earth, we find life.

Want to learn more about Saturn?

We’ve recorded two episodes of Astronomy Cast just about Saturn. The first is Episode 59: Saturn, and the second is Episode 61: Saturn’s Moons.

June 2, 2013December 23, 2015 by Jason Major

A Ghostly “Ladder” in Saturn’s F Ring

A ladder-like structure in Saturn's F ring seen by Cassini on Feb. 13, 2013 (NASA/JPL-Caltech/SSI)

Saturn’s F ring is certainly a curious structure. Orbiting the giant planet 82,000 kilometers above its equatorial cloud tops, the F ring is a ropy, twisted belt of bright ice particles anywhere from 30-500 km wide. It can appear as a solid band or a series of braided cords surrounded by a misty haze, and often exhibits clumps and streamers created by the gravitational influence of embedded moonlets or passing shepherd moons.

In the picture above, acquired by the Cassini spacecraft on Feb. 13, 2013 and released on May 27, we see a section of the F ring separated into long ropes and spanned by connecting bands of bright material — the “ladder” structure suggested in the title.

Scientists believe that interactions between the F ring and the moons Prometheus and Pandora cause the dynamic structure of the F ring. (Watch an animation of the F ring and shepherd moons here.)

Made of particles of water ice finer than cigarette smoke, the F ring orbits Saturn beyond the outer edge of the A ring across the expanse of the 2,600-km-wide Roche Division. In these images, Saturn and the main ring systems are off frame to the left.

Detail of ladder structure in the F ring

This view looks toward the unilluminated side of the rings from about 32 degrees below the ringplane. The image was taken in visible light with the Cassini spacecraft’s narrow-angle camera (NAC).

The view was obtained at a distance of approximately 426,000 miles (686,000 kilometers) from Saturn and at a phase angle of 162 degrees. Image scale is 2 miles (4 kilometers) per pixel.

Source: NASA/JPL’s Cassini mission site.

May 29, 2013December 23, 2015 by Nancy Atkinson

Saturn’s Moon Dione May Have Been Active Like Enceladus

Saturn's moon Dione, as seen by the Cassini spacecraft. Credit: NASA/JPL-Caltech/Space Science Institute

From a JPL press release:

From a distance, most of the Saturnian moon Dione resembles a bland cueball. Thanks to close-up images of a 500-mile-long (800-kilometer-long) mountain on the moon from NASA’s Cassini spacecraft, scientists have found more evidence for the idea that Dione was likely active in the past. It could still be active now.

“A picture is emerging that suggests Dione could be a fossil of the wondrous activity Cassini discovered spraying from Saturn’s geyser moon Enceladus or perhaps a weaker copycat Enceladus,” said Bonnie Buratti of NASA’s Jet Propulsion Laboratory in Pasadena, Calif., who leads the Cassini science team that studies icy satellites. “There may turn out to be many more active worlds with water out there than we previously thought.”

Janiculum Dorsa, a mountain that appears as the long, raised scar in the middle of this Cassini image, is providing new evidence that the Saturnian moon Dione was recently active. Credit: NASA/JPL-Caltech/Space Science Institute.

Other bodies in the solar system thought to have a subsurface ocean – including Saturn’s moons Enceladus and Titan and Jupiter’s moon Europa – are among the most geologically active worlds in our solar system. They have been intriguing targets for geologists and scientists looking for the building blocks of life elsewhere in the solar system. The presence of a subsurface ocean at Dione would boost the astrobiological potential of this once-boring iceball.

Hints of Dione’s activity have recently come from Cassini, which has been exploring the Saturn system since 2004. The spacecraft’s magnetometer has detected a faint particle stream coming from the moon, and images showed evidence for a possible liquid or slushy layer under its rock-hard ice crust. Other Cassini images have also revealed ancient, inactive fractures at Dione similar to those seen at Enceladus that currently spray water ice and organic particles.

The mountain examined in the latest paper — published in March in the journal Icarus — is called Janiculum Dorsa and ranges in height from about 0.6 to 1.2 miles (1 to 2 kilometers). The moon’s crust appears to pucker under this mountain as much as about 0.3 mile (0.5 kilometer).

The topography of a mountain known as Janiculum Dorsa on the Saturnian moon Dione. Color denotes elevation, with red as the highest area and blue as the lowest. Credit: NASA/JPL-Caltech/Space Science Institute.

“The bending of the crust under Janiculum Dorsa suggests the icy crust was warm, and the best way to get that heat is if Dione had a subsurface ocean when the ridge formed,” said Noah Hammond, the paper’s lead author, who is based at Brown University, Providence, R.I.

Dione gets heated up by being stretched and squeezed as it gets closer to and farther from Saturn in its orbit. With an icy crust that can slide around independently of the moon’s core, the gravitational pulls of Saturn get exaggerated and create 10 times more heat, Hammond explained. Other possible explanations, such as a local hotspot or a wild orbit, seemed unlikely.

Scientists are still trying to figure out why Enceladus became so active while Dione just seems to have sputtered along. Perhaps the tidal forces were stronger on Enceladus, or maybe the larger fraction of rock in the core of Enceladus provided more radioactive heating from heavy elements. In any case, liquid subsurface oceans seem to be common on these once-boring icy satellites, fueling the hope that other icy worlds soon to be explored – like the dwarf planets Ceres and Pluto – could have oceans underneath their crusts. NASA’s Dawn and New Horizons missions reach those dwarf planets in 2015.

May 22, 2013December 23, 2015 by Nancy Atkinson

Cassini Flyby Will Look for Waves on Titan’s Seas

A dense network of small rivers or swampy areas appears to connect some of the seas on Saturn's moon Titan, as seen in this comparison of data of the same area from two instruments on NASA's Cassini spacecraft. Images from the radar instrument are on the left and images from the visual and infrared mapping spectrometer (VIMS) are on the right. Credit: NASA/JPL-Caltech/University of Arizona

Are there waves on Titan’s lakes and seas? Cassini scientists say that the best chance of answering this question is with the May 23 flyby of Titan, when the Cassini spacecraft will be just 970 km (603 miles) over Titan’s biggest ‘lake,’ the northern sea named Ligeia Mare.

Lakes, seas, and rivers were discovered on Titan by Cassini in 2005, and since then, scientists and space enthusiasts have been intrigued about the possibility of what could be found in these bodies of hydrocarbon liquid. Future potential missions such as paddleboats have even been proposed.

Lakes, seas and rivers of liquid hydrocarbons cover much of the Titan’s northern hemisphere. Additionally, these hydrocarbons may rain down on the surface. The questions is, are these frigid liquid bodies capable of producing wave action, or would they be a rigid type of frigid? With surface temperature at -178 degrees Celsius (-289 degrees Fahrenheit), Titan’s environment is too cold for life as we may know it, but its environment, rich in the building blocks of life, is of great interest to astrobiologists.

Additionally, new models of Titan’s atmosphere prediction that as the seasons change in Titan’s northern hemisphere, waves could ripple across the moon’s hydrocarbon seas, and possibly even hurricanes could begin to swirl over these areas, too. The model predicting waves tries to explain data from the moon obtained so far by Cassini.

“If you think being a weather forecaster on Earth is difficult, it can be even more challenging at Titan,” said Scott Edgington, Cassini’s deputy project scientist at NASA’s Jet Propulsion Laboratory, Pasadena, Calif. “We know there are weather processes similar to Earth’s at work on this strange world, but differences arise due to the presence of unfamiliar liquids like methane. We can’t wait for Cassini to tell us whether our forecasts are right as it continues its tour through Titan spring into the start of northern summer.”

For the flyby on May 23, the altimetry data that will be collected by the radar instrument could show whether the surface of that sea is thick like molasses or as thin as liquid water on Earth.

In addition, radar will look for changes in small northern lakes last observed in previous flybys, the T-16 and T-19 flybys.
This flyby is a carefully planned sibling of the following flyby; the combination of the data from T-91 and T-92 will provide stereo views of the same geography, which will tell us about the depth of the lake walls.

Stay tuned! See the Cassini flyby page for more info, and read more about the new models of Titan’s atmosphere here.

May 8, 2013December 23, 2015 by Elizabeth Howell

Trapped Gas Explains Saturn’s Fresh Face

Saturn seen by the Cassini spacecraft in late 2012. If you look carefully, you can spot the shadow of Mimas in the image. Credit: NASA/JPL-Caltech/Space Science Institute

The mystery of Saturn’s bright, youthful appearance is a step closer to resolution. And it actually has to do with gas.

Layers of gas within the ringed giant trap heat emanating from the center, preventing the planet from cooling off as it was expected to do as it aged, according to a model developed by a European science team.

“Scientists have been wondering for years if Saturn was using an additional source of energy to look so bright, but instead our calculations show that Saturn appears young because it can’t cool down,” stated Gilles Chabrier, a physics and astronomy professor at the University of Exeter and part of the research team.

“Instead of heat being transported throughout the planet by large scale (convective) motions, as previously thought, it must be partly transferred by diffusion across different layers of gas inside Saturn. These separate layers effectively insulate the planet and prevent heat from radiating out efficiently. This keeps Saturn warm and bright.”

A raw image of Saturn taken May 4, 2013, as seen through the eyes of the Cassini probe. Credit: NASA/JPL/Space Science Institute

You can also see layered convection on Earth, pointed out scientists. In this instances, salty water stays underneath colder and less salty liquid. The salt trap stops water from moving between the layers, also stopping heat from transferring.

The findings were published in Nature Geoscience and included participation from the University of Exeter in England and the Ecole Normale Supérieure de Lyon in France.

Source: University of Exeter

May 3, 2013December 23, 2015 by Elizabeth Howell

How Saturn’s Magnetic Activity Could Help us Pinpoint Time on the Ringed Planet

Image of Saturn’s aurora seen at ultraviolet wavelengths. The spiral shape seen here is similar to the distorted radio aurora visualised by the team and also indicates enhanced auroral activity. Credit: ESA/NASA/Hubble

He’s not even finished his first university degree yet, but Tim Kennelly is already part of a team that is altering our perception of time on Saturn.

The University of Iowa undergrad — in junior year, yet — led a paper describing activity in Saturn’s magnetosphere, where charged particles collect and sometimes form auroras. The process changes with the Saturnian seasons and could, the university stated, help scientists better understand how long a Saturn day lasts.

The researchers used information from NASA’s Cassini spacecraft, which has been orbiting the planet and its moons since 2004. The research challenge: Saturn is a gas giant full of layers that each have their own rotational speed. That makes it hard to figure out how long Saturn’s day is. (It’s about 10 hours, but varies by latitude.)

Kennelly made direct observations of seasonal changes in a phenomenon known as Saturn kilometric radiation (SKR). This robust radio signal was first discovered several decades ago and is being examined more closely by Cassini.

“UI space physicist Donald Gurnett and other scientists showed that the north and south poles have their own SKR ‘days’ that vary over periods of weeks and years,” the university stated. “How these different periods arise and are driven through the magnetosphere has become a central question of the Cassini mission, according to NASA officials.”

Kennelly observed, from looking at data collected between 2004 and 2011, that SKAs are linked with “flux tubes” that are made up of plasma, or superhot gas. These tubes happen around the same time of instances of SKAs in the northern and southern hemisphere, which changes seasonally.

It’s possible that this understanding could be carried over to other planets, the university stated, including our own.

“This finding may alter how scientists look at the Earth’s magnetosphere and the Van Allen radiation belts that affect a variety of activities at Earth ranging from space flight safety to satellite and cell phone communications,” it added.

This won’t be Kennelly’s only degree. He is about to apply to graduate schools, and he has aims to earn a doctorate in plasma physics.

“I’m pleased to have contributed to our understanding of Saturn’s magnetosphere so early in my career,” stated Kennelly. “I hope this trend continues.”

The research is described in the American Geophysical Union’s Journal of Geophysical Research.

Source: University of Iowa

April 29, 2013December 23, 2015 by Elizabeth Howell

Saturn Storm’s ‘Suck Zone’ Shown In Spectacular Cassini Shots

A false-color image, taken by the Cassini spacecraft, of a huge hurricane at Saturn's north pole. Credit: NASA/JPL-Caltech/SSI

Checking out the above pictures of a Saturn hurricane, one can’t help but wonder: how close was the Cassini spacecraft to spiralling down into gassy nothingness?

These dizzying images of a hurricane on Saturn, of course, came as the spacecraft zoomed overhead at a safe distance. NASA’s goal in examining this huge hurricane is to figure out its mechanisms and to compare it to what happens on our home planet.

Hurricanes on Earth munch on water vapor to keep spinning. On Saturn, there’s no vast pool of water to draw from, but there’s still enough water vapor in the clouds to help scientists understand more about how hurricanes on Earth begin, and continue.

“We did a double take when we saw this vortex because it looks so much like a hurricane on Earth,” stated Andrew Ingersoll, a Cassini imaging team member at the California Institute of Technology in Pasadena. “But there it is at Saturn, on a much larger scale, and it is somehow getting by on the small amounts of water vapor in Saturn’s hydrogen atmosphere.”

A false-color view of Saturn's storm, as seen through Cassini's wide-angle camera. The blue bands at the edge are Saturn's rings. Credit: NASA/JPL-Caltech/SSI — A false-color view of Saturn’s storm, as seen through Cassini’s wide-angle camera. You can see the eye in dark red, the jet stream in yellowish-green, and low-lying clouds in orange. The blue bands at the edge are Saturn’s rings. Credit: NASA/JPL-Caltech/SSI

There’s one big change in hurricane activity you’d observe if suddenly shifted from Earth to Saturn: this behemoth — 1,250 miles (2,000 kilometers) wide, about 20 times its Earthly counterparts — spins a heckuva lot faster.

In the eye, winds in the wall speed more than four times faster than what you’d find on Earth. The hurricane also sticks around at the north pole. On Earth, hurricanes head north (and eventually dissipate) due to wind forces generated by the planet’s rotation.

“The polar hurricane has nowhere else to go, and that’s likely why it’s stuck at the pole,” stated Kunio Sayanagi, a Cassini imaging team associate at Hampton University in Hampton, Va.

Cassini initially spotted the storm in 2004 through its heat-seeking infrared camera, when the north pole was shrouded in darkness during winter.

The spacecraft first caught the storm in visible light in 2009, when NASA controllers altered Cassini’s orbit so that it could view the poles.

Saturn, of course, is not the only gas giant in the solar system with massive hurricanes. Jupiter’s Great Red Spot has been raging since before humans first spotted it in the 1600s. It appears to be shrinking, and could become circular by 2040.

Neptune also has hurricanes that can reach speeds of 1,300 miles (2,100 kilometers) an hour despite its cold nature; it even had a Great Dark Spot spotted during Voyager’s flypast in 1989 that later faded from view. Uranus, which scientists previously believed was quiet, is a pretty stormy place as well.

Check out this YouTube video for more details on how Saturn’s storm works.

Source: Jet Propulsion Laboratory

April 28, 2013December 30, 2015 by Nancy Atkinson

Saturn Reaches Opposition on April 28

Saturn is one of the most striking objects to see through a telescope, and it is now at its brightest in the night sky as it reaches opposition from the Sun. This is when Earth stands mostly perfectly in line between Saturn and the Sun. It is when Saturn is brightest (at magnitude +0.3), closely approximating famous “first magnitude” stars like Betelgeuse. Also, it is when Saturn is out all night long. Continue reading “Saturn Reaches Opposition on April 28”

April 25, 2013December 23, 2015 by Nancy Atkinson

Cassini Watches as Meteors Hit Saturn’s Rings

ive images of Saturn's rings, taken by NASA's Cassini spacecraft between 2009 and 2012, show clouds of material ejected from impacts of small objects into the rings. Image Credit: NASA/JPL-Caltech/Space Science Institute/Cornell.

From tell-tale evidence, we know that Earth, our Moon and other bodies in our Solar System are constantly barraged with both small meteoroids and larger asteroids or comets. And sometimes – like in the case of seeing meteors fling across our sky, or flashes on the Moon or Jupiter getting hit by Comet Shoemaker-Levy 9 — we even get to watch as it happens. Now, for the first time the Cassini spacecraft has provided direct evidence of small meteoroids crashing into Saturn’s rings.

Researchers say that studying the impact rate of meteoroids from outside the Saturnian system helps scientists understand how different planet systems in our solar system formed.

Saturn’s rings act as very effective detectors of many kinds of surrounding phenomena, including the interior structure of the planet and the orbits of its moons. For example, a subtle but extensive corrugation that ripples 12,000 miles (19,000 kilometers) across the innermost rings tells of a very large meteoroid impact in 1983.

“These new results imply the current-day impact rates for small particles at Saturn are about the same as those at Earth — two very different neighborhoods in our solar system — and this is exciting to see,” said Linda Spilker, Cassini project scientist at NASA’s Jet Propulsion Laboratory in Pasadena, Calif. “It took Saturn’s rings acting like a giant meteoroid detector — 100 times the surface area of the Earth — and Cassini’s long-term tour of the Saturn system to address this question.”

The Saturnian equinox in summer 2009 was an especially good time to see the debris left by meteoroid impacts. The very shallow sun angle on the rings caused the clouds of debris to look bright against the darkened rings in pictures from Cassini’s imaging science subsystem.

This animation depicts the shearing of an initially circular cloud of debris as a result of the particles in the cloud having differing orbital speeds around Saturn. Image credit: NASA/Cornell

“We knew these little impacts were constantly occurring, but we didn’t know how big or how frequent they might be, and we didn’t necessarily expect them to take the form of spectacular shearing clouds,” said Matt Tiscareno, lead author of the paper and a Cassini participating scientist at Cornell University in Ithaca, N.Y. “The sunlight shining edge-on to the rings at the Saturnian equinox acted like an anti-cloaking device, so these usually invisible features became plain to see.”

Tiscareno and his colleagues now think meteoroids of this size probably break up on a first encounter with the rings, creating smaller, slower pieces that then enter into orbit around Saturn. The impact into the rings of these secondary meteoroid bits kicks up the clouds. The tiny particles forming these clouds have a range of orbital speeds around Saturn. The clouds they form soon are pulled into diagonal, extended bright streaks.

“Saturn’s rings are unusually bright and clean, leading some to suggest that the rings are actually much younger than Saturn,” said Jeff Cuzzi, a co-author of the paper and a Cassini interdisciplinary scientist specializing in planetary rings and dust at NASA’s Ames Research Center in Moffett Field, Calif. “To assess this dramatic claim, we must know more about the rate at which outside material is bombarding the rings. This latest analysis helps fill in that story with detection of impactors of a size that we weren’t previously able to detect directly.”

Source: JPL

April 25, 2013December 23, 2015 by Jason Major

Saturn’s Little Wavemaking Moon

Daphnis' gravity disturbs the edges of the Keeler Gap as it travels along

Captured on January 15, this narrow-angle Cassini image shows an outer portion of Saturn’s A ring on the left and the ropy F ring crossing on the right. The thin black line near the A ring’s bright edge is the Keeler Gap, a 22-mile-wide space cleared by the passage of Daphnis, a shepherd moon barely 5 miles (about 7.5 km) across. As it travels around Saturn within the gap its gravity perturbs the fine icy particles within the rings, sending up rippling waves both before and behind it — visible here near the upper center.

From Cassini’s distance of 870,000 miles (1.4 million km) Daphnis itself is just barely visible as a single pixel within the Gap — can you see it? If not, click below…

There it is:

Highlighting Daphnis inside the Keeler Gap

While lacking the murky mystery of Titan’s atmosphere, Enceladus’ dramatic jets and the tortured and cratered surfaces found on Dione, Rhea, Mimas and many of Saturn’s larger icy moons, little Daphnis has always fascinated me because of the scalloped waves it kicks up within Saturn’s rings. Eventually these waves settle back down, but at their highest they can extend a mile or two above and below the ring plane!

Daphnis' wake casts peaked shadows on the rings — Daphnis’ wake casts peaked shadows on the rings

This effect was most pronounced during Saturn’s spring equinox in August 2009 when sunlight was striking the rings edge-on, creating strong shadows from any areas of relief.

Imagine the impressive view you’d have if you were nearby, positioned just above the rings as Daphnis approached and hurtled past, the rings rising up in mile-high peaks from the moon’s gravity before smoothing out again. Incredible!

Daphnis seen by Cassini in June 2010 (NASA/JPL/SSI)

And I’m not the only one to imagine such a scene either — apparently artist Erik Svensson is also intrigued by Daphnis, enough to have been inspired to create the image below. How very cool!

Future explorers watch Daphnis speed past at the edge of Saturn's A ring (© Erik Svennson, all rights reserved. Used with permission.) — Future explorers watch Daphnis speed past at the edge of Saturn’s A ring (© Erik Svennson, all rights reserved. Used with permission.)

Like its larger shepherd moon sister Prometheus, Daphnis may be little but still has a big effect on the icy stuff that makes up Saturn’s iconic rings.

And for lots more views of Daphnis click here (but watch out, it may just become your favorite moon too!)

Image credits: NASA/JPL-Caltech/Space Science Institute.